A. Field of the Invention
The subject invention relates generally to fiber optic devices using evanescent-wave coupling, and more specifically to star couplers in which the optical waveguides are embedded in a rigid substrate.
B. Description of the Prior Art
Those concerned with transmission of information through optical waveguides have frequently desired to transfer information from one waveguide to another. One method of transferring information from one optical waveguide to another involves evanescent-wave coupling in which two waveguides are placed in close juxtaposition to one another. When light is transmitted through one waveguide, it is not completely contained within that waveguide, but rather is partially dispersed into the second waveguide so that evanescent-wave coupling occurs.
In other applications, it is desirable to transfer light simultaneously from one waveguide to a plurality of other waveguides. One method of transferring light to a plurality of waveguides is to use a star coupler configuration in which a plurality of waveguides are twisted about each other to allow evanescent coupling to occur. One limitation of such couplers is that it may be difficult to control the amount of coupling that occurs from one fiber to another in a twisted fiber configuration. Another problem with such a coupler is that star couplers having a twisted fiber configuration are somewhat fragile.